In crop production, there is a steady demand for stable production of high-quality plants and reduction of pesticide dependency. To that end, researchers are actively improving, breeding, and developing cultivars of plants resistant to pests and pathogenic microbes through useful plant biotechnologies, such as plant cell fusion and recombinant DNA techniques. Transformed plants resistant to herbicides (Japanese Patent Application Kokai Publication No. (JP-A) H02-186925 (unexamined, published Japanese patent application)), viruses (JP-A (Kokai) H04-330233), and pests (JP-A (Kokai) H03-247220) have already been produced using recombinant DNA techniques. Furthermore, several types of transformed plants resistant to plant pathogenic microbes have been produced, for example, transformed plants showing resistance to a pathogenic filamentous fungus, which are produced by introducing a gene of an enzyme that inactivates a toxin produced by the pathogenic fungus (Windhovel, U. et al., Plant Physiol., 104, 119-125 (1994)); transformed plants showing resistance to at least one pathogenic bacterium, which are produced by introducing a gene of an insect-derived antibacterial protein (JP-A (Kokai) H07-250685); transformed plants resistant to complex disease, which are produced by introducing a Japanese mustard spinach-derived gene (JP-A (Kokai) 2004-329215); transformed plants resistant to multiple diseases, which are produced using the thionine gene (JP-A (Kokai) 2003-88379); and transformed plants resistant to complex diseases, which are produced using an acidic thaumatin-like protein gene (JP-A (Kokai) 2003-199448). However, the introduction of these defense genes into plants did not confer sufficiently strong resistance to multiple pathogens. Furthermore, some of the introduced genes have harmful effects on the growth, fertility, and such of the transformants, thereby hindering their practical application.
WRKY transcription factors have been reported to be involved in disease resistance of dicots such as Arabidopsis (Kalde, M. et al., Mol. Plant Microbe Interact., 16, 295-305 (2003); Li, J. et al., Plant Cell, 16, 319-331 (2004); Robatzek, S. et al., Genes Dev., 16, 1139-1149 (2002); Yu, D. et al., Plant Cell, 13, 1527-1540 (2001); Chen, C. et al., Plant Physiol., 129, 706-716 (2002)). Several OsWRKY genes that confer disease resistance in rice plants have been reported in recent years (Xie, Z. et al., Plant Physiol., 137, 176-189 (2005); Qiu, Y. et al., Chinese Science Bulletin, 49(20), 2159-2168 (2004); Qiu, D. et al., Mol Plant Microbe Interact, 20(5), 492-499 (2007); Liu, X. et al., J Plant Physiol, 164(8), 969-979 (2007); Chujo, T. et al., Biochimica et Biophysica Acta (BBA)—Gene Structure and Expression, 1769(7-8), 497-505 (2007); Chujo, T. et al., Biosci Biotechnol Biochem, 72(1), 240-245 (2008); Tao, Z. et al., Plant Phys., 151, 936-948 (2009); Qiu, Y. and D. Yu, Environmental and Experimental Botany, 65(1), 35-47 (2009)). The transcription factor WRKY45 of rice (OsWRKY45) is known to confer a significantly strong resistance to rice blast, bacterial leaf blight, and the like (a complex disease resistance). WRKY45 has also been reported in wheat (TaWRKY45) (Bahrini et al., Breeding Science 61: 121-129 (2011); Bahrini et al., Breeding Science 61: 319-326 (2011)). When OsWRKY45 is expressed using the maize ubiquitin (Zmubi) promoter (PZmUbi) which is a strong constitutive promoter, the rice shows a strong complex disease resistance to rice blast, bacterial leaf blight, and brown spot (WO 2006/126671). However, in the WRKY45-expressing rice, growth delay and decrease in the rice grain yield are observed (Shimono, M. et al., Plant Cell, 19, 2064-2076 (2007)), suggesting that overexpression of the WRKY45 gene may have resulted in problems of deterioration of rice growth and yield.
Cis elements that are known to influence modulation of gene expression include transcriptional promoters, transcriptional/translational enhancers, transcriptional terminators, and such. In an attempt to balance complex disease resistance and agronomic traits, techniques of expressing WRKY45 using the OsUbil, EF1a, and OsUbi7 promoters which have a weaker constitutive activity (WO 2012/121093) have been developed. Besides these promoters, many promoters are known as transcriptional promoters, and examples include the promoter of glutathione-S-transferase (GST) gene and the promoter of one of the PR protein genes (PR1b promoter). The PR1b promoter is a promoter induced upon infection by a pathogenic microorganism, and there have been reports that driving the expression of Xanthomonas oryzae pv. oryzae (Xoo)-resistance gene by this promoter resulted in resistance against Xoo (Gu et al., Nature, Vol 435, 23 Jun. 2005, 1122-1125 (2005); Tian and Yin, Molecular Plant Pathology, Vol 10(1), 29-39 (2009)). As an example of the translational enhancers, the 5′-UTR of the rice alcohol dehydrogenase (OsADH) gene is known (Sugio T et al., Journal of Bioscience and Bioengineering, Vol. 105, No. 3, 300-302 (2008)). Further, it has been reported that the UTRs of the tobacco and Arabidopsis ADH genes can be used as translational enhancers (Satoh, J. et al., Journal of bioscience and bioengineering, 98, 1-8 (2004); Nagaya, S. et al, Plant Cell Physiol., 46 (3), 438-444 (2005)). Examples of transcriptional terminators include the 35S terminator (35ST) of the Cauliflower mosaic virus (CaMV) and the terminator of Nopaline synthase (Nos) gene.